1. Field of the Invention
The present invention relates to an optical system for viewing an object and for detecting certain aspects relating thereto such as the extent of its dimensions in two directions.
2. Description of the Prior Art
It is often desirable to determine the characteristics of an object in order to obtain information, for example, concerning its shape or its orientation with respect to a background. In the art of labelling, containers such as bottles having irregular shapes often have labels fastened thereon which also may be of irregular shape and it is desirable to be able to determine that the label is in a proper position with respect to the bottle. One way of determining whether the label is in the correct position is to observe the bottle and the label with a plurality of radiation responsive detectors which will produce individual outputs dependent upon whether the bottle or the label is in the field of view with respect to a background. In the prior art, bottles with labels affixed thereto have been moved along a conveyor belt so as to pass a linear array of detectors which are mounted adjacent the conveyor belt, usually perpendicular to the bottle motion. The image of the moving bottle is directed on to the detectors so that the outputs of the detectors will change when the bottle comes into the field of view and then change again when the label comes into the field of view, thus giving a one-dimensional indication of the extent of the bottle and label because the detectors, being spaced vertically, will be activated by the bottle and the label so that it can be determined from the number of detectors that are activated, what the vertical dimensions of the bottle and label are. Of course, it is desirable to determine the vertical dimensions of the bottle and label at a plurality of horizontal positions in order to determine whether the label is fixed in the desired position. In order to do this, some synchronizing means has, in the past, been necessary so as to provide a signal indicative of the position of the bottle as it moves along the conveyor belt. Then, with successive vertical readings from the detectors, an indication of the orientation of the label on the bottle may be obtained. For example, a plurality of photo cells may be spaced in a horizontal direction beside the belt and, as the bottle eclipses successive photo cells, their outputs can be used to produce horizontal position indications as the bottle moves past them and the system will thus have an indication of where the bottle is at any particular moment. Alternately, the conveyor belt may be controlled to move at a predetermined rate so that the position of the bottle is known from its initial placement on the conveyor belt and by timing the speed of the conveyor belt as it moves past the detector array.
Several difficulties have been encountered with the prior art systems. For example, with the speed control systems, the bottle may slip with respect to the conveyor belt and thus throw all of the measurements off. With the photo cell systems, different size bottles require that the photo electric detectors be repositioned for each different size in order to now provide the proper position signals.